Heretofore, there have been proposed various apparatuses of electromagnetic transfer type (electromagnetic induction type), a resistive film type, an ultrasonic type, etc. Of these apparatuses, the electromagnetic induction type apparatuses have been proposed in European Patent Applications Nos. EP0716390A1, and EP0740266A2, in which a position detection surface at which a plurality of loop coils are arranged in parallel and a position indicator such as a pen or a cursor are employed, and the loop coils are used as sensors, i.e., antennas and arranged in an X-direction and a Y-direction at a pair of sensor surfaces orthogonal to each other and utilize a magnetic interaction with a coil or a resonant circuit incorporated in the position indicator (pen) to transfer an electromagnetic wave therebetween, so that on the basis of a detected signal, a coordinate and other information on the position indicator are detected. The sensor substrate on which the loop coils (antennas) are disposed on the back side of a liquid crystal panel, and the pen is moved on the front surface of the liquid crystal panel, so that a position of the pen is detected and a trail of the moved pen can be displayed on the liquid crystal picture area.
On the other hand, in recent years, as a display screen, electronic papers of an electro-luminescent (EL) type or an electrophoretic type described in U.S. Pat. No. 6,130,774 have been proposed. In these electronic papers, it is possible to provide flexibility to the entire display apparatuses by development of an organic EL material or an organic thin film transistor (TFT). As a result, it becomes possible to realize a so-called flexible display which is thin and can be bent and curled.
In the above described electromagnetic type apparatus, it is also possible to form the sensor substrate, provided with the loop coils, of a material consisting of a polyimide film having a thickness of, e.g., about 0.4 mm. As a result, the sensor substrate also has flexibility. Accordingly, it is possible to realize a display apparatus provided with a pen input tool by using various electronic papers (of EL type or electrophoretic type) and the electromagnetic induction type apparatus in combination. The resultant display apparatus can be bent or rolled when it is carried or held.
However, such a pen input type display apparatus has accompanied with the following problems.
In the case where the pen input is performed in such a state that the pen input type display apparatus is held with hand, not placed on a desktop, an input surface portion is deformed due to flexibility of the apparatus when a pen is moved on the input surface portion. As a result, it is impossible to input a character or a graphic pattern in a desired shape. In this regard, it is also possible to effect input with such a force that the input surface is not deformed by lowering the pen pressure. However, even in such a case, it is difficult to input the character or graphic pattern in the desired shape. The input can be performed when the pen input display apparatus is placed on a hard or rigid underlay such as a book. However, carrying of the underlay at all times is very troublesome.
Further, even when the pen input display apparatus is used as a flexible display, flexibility thereof at all times causes an inconvenience in some cases.